Converting from 6EU7 to 12AX7 ... need a little help.

sangandongo · 03-28-2009, 08:42 PM

Hi everyone.

As the title suggests, I want to convert an amp with a 6EU7 to a 12AX7. I have a nearly limitless supply of vintage 12AX7s but very few 6EU7s.

I've found the pinouts on tdsl and made a little conversion chart for my own benefit. The one question I have is that the 12AX7's 9th pin is designated as the center heater pin but there's no correlating pin on the 6EU7, so I don't know where to go with that.

Below is the chart I made for myself.

I'm doing this to a '65 Gibson Skylark GA-5T. I have the schematics for that up on my site as well if anyone wants them.

Thanks for any help you can offer, I greatly appreciate it.

tubeswell · 03-28-2009, 11:33 PM

When running a 12AX7 on a 6.3V heater winding, pins 4 & 5 are tied together on one side of the heater winding, and pin 9 is on the other side of the heater winding. So you need to run one wire from pins 4-5 of the 12AX7 to either pin 1 or pin 2 of the 6EU7, and the other wire from pin 9 of the 12AX7 to the other pin (2 or 1) conversely.

sangandongo · 03-29-2009, 12:10 AM

So, if I understand you correctly, the correlation would be like this (using the relationship table on my chart). Makes sense to me if that's right.

12ax7 - 6eu7
1 = 6
2 = 5
3 = 4
4,5 = 2
6 = 7
7 = 8
8 = 9
9 = 1

Thanks for the answer so quickly, by the way.

--
John

tubeswell · 03-29-2009, 10:10 AM

Sounds about right if you've got the pins numbers right. Check here
http://www.triodeel.com/6eu7p1.gif

Roland · 05-01-2009, 11:37 PM

Quote:

Originally Posted by sangandongo

So, if I understand you correctly, the correlation would be like this (using the relationship table on my chart). Makes sense to me if that's right.

12ax7 - 6eu7
1 = 6
2 = 5
3 = 4
4,5 = 2
6 = 7
7 = 8
8 = 9
9 = 1

Thanks for the answer so quickly, by the way.

--
John

Did this work out for you?

I am contemplating the same thing in a Minuteman GA-20RVT

Your help appreciated in advance.

thanx

sangandongo · 05-02-2009, 04:57 AM

Yes and no.

The OT was actually dead, so even though I rewired the preamp section for 12AX7, the amp ended up shitting itself anyhow. SO, yes, it worked and sounded great for a few minutes, but the real issue was the output tranny, so I'm going to have to rewire that in later.

--
j.k.

03-28-2009, 08:42 PM	#1
sangandongo Junior Member Join Date: Jan 2009 Posts: 3	Converting from 6EU7 to 12AX7 ... need a little help. Hi everyone. As the title suggests, I want to convert an amp with a 6EU7 to a 12AX7. I have a nearly limitless supply of vintage 12AX7s but very few 6EU7s. I've found the pinouts on tdsl and made a little conversion chart for my own benefit. The one question I have is that the 12AX7's 9th pin is designated as the center heater pin but there's no correlating pin on the 6EU7, so I don't know where to go with that. Below is the chart I made for myself. I'm doing this to a '65 Gibson Skylark GA-5T. I have the schematics for that up on my site as well if anyone wants them. Thanks for any help you can offer, I greatly appreciate it.

03-28-2009, 11:33 PM	#2
tubeswell Supporting Member Join Date: Feb 2007 Location: Wellington NZ Posts: 2,662	When running a 12AX7 on a 6.3V heater winding, pins 4 & 5 are tied together on one side of the heater winding, and pin 9 is on the other side of the heater winding. So you need to run one wire from pins 4-5 of the 12AX7 to either pin 1 or pin 2 of the 6EU7, and the other wire from pin 9 of the 12AX7 to the other pin (2 or 1) conversely. __________________ Building a better world (one tube amp at a time)

03-29-2009, 10:10 AM	#4
tubeswell Supporting Member Join Date: Feb 2007 Location: Wellington NZ Posts: 2,662	Sounds about right if you've got the pins numbers right. Check here http://www.triodeel.com/6eu7p1.gif __________________ Building a better world (one tube amp at a time)

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03-29-2009, 12:10 AM	#3
sangandongo Junior Member Join Date: Jan 2009 Posts: 3	So, if I understand you correctly, the correlation would be like this (using the relationship table on my chart). Makes sense to me if that's right. 12ax7 - 6eu7 1 = 6 2 = 5 3 = 4 4,5 = 2 6 = 7 7 = 8 8 = 9 9 = 1 Thanks for the answer so quickly, by the way. -- John

05-02-2009, 04:57 AM	#6
sangandongo Junior Member Join Date: Jan 2009 Posts: 3	Yes and no. The OT was actually dead, so even though I rewired the preamp section for 12AX7, the amp ended up shitting itself anyhow. SO, yes, it worked and sounded great for a few minutes, but the real issue was the output tranny, so I'm going to have to rewire that in later. -- j.k.

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